NZ Transport Agency Requiring Authority · MacKays to Peka Peka Expressway Proposal ... 5 I have...

Statement of evidence of Gavin Alexander (Ground Settlement) for the

NZ Transport Agency

Dated: 3 September 2012

REFERENCE: John Hassan ([email protected])

Suzanne Janissen ([email protected])

Before a Board of Inquiry

MacKays to Peka Peka Expressway Proposal

under: the Resource Management Act 1991

in the matter of: Notice of requirement for designation and resource

consent applications by the NZ Transport Agency for the

MacKays to Peka Peka Expressway Proposal

applicant: NZ Transport Agency

Requiring Authority

Chapman TrippT: +644499 5999F: +644472 7111

10 Customhouse QuayPO Box 993, Wellington 6140NewZealand

www.chapmantripp.comAuckland, Wellington,Christchurch

CHAPMAN~TR/PP~

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TABLE OF CONTENTS

QUALIFICATIONS AND EXPERIENCE ..................................................2

SCOPE OF EVIDENCE ..........................................................................4

EXECUTIVE SUMMARY ........................................................................5

BACKGROUND AND ROLE....................................................................6

GROUND CONDITIONS .......................................................................8

ASSESSMENT OF GROUND SETTLEMENT EFFECTS ............................10

Sources of settlement effects ........................................................... 10

Methodology of calculating settlement effects ...................................... 12

Settlement Estimates and Effects ...................................................... 13

Monitoring .................................................................................... 15

Mitigation and remediation ............................................................... 15

RESPONSE TO SUBMISSIONS ...........................................................16

Ground settlement issues ................................................................ 16

Building on sand and peat ................................................................ 18

Earthquakes and liquefaction ............................................................ 18

RESPONSE TO THE BOI’S SECTION 92 REQUEST ..............................19

PROPOSED CONDITIONS ..................................................................22

CONCLUSIONS ..................................................................................23

ANNEXURE A: PREDICTED SETTLEMENT PLANS - APPENDIX 35.G, TECHNICAL REPORT

35 ............................................................................................... 25

ANNEXURE B: PROPOSED CONDITIONS ....................................................... 26

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STATEMENT OF EVIDENCE OF GAVIN ALEXANDER FOR THE NZ

TRANSPORT AGENCY

QUALIFICATIONS AND EXPERIENCE

1 My full name is Gavin John Alexander. I am a Technical Director in

Beca Infrastructure Limited‟s (Beca) Geotechnical Group based in

Auckland.

2 I have the following qualifications and experience relevant to the

evidence I shall give:

2.1 I hold a Bachelor of Civil Engineering from the University of

Auckland (1986) and a Masters Degree in Soil Mechanics and

Engineering Seismology from Imperial College, University of

London (1991).

2.2 I am a New Zealand Chartered Professional Engineer, a Fellow

of the Institution of Professional Engineers of New Zealand,

and a Member of the New Zealand Geotechnical, Structural

Engineering and Large Dam Societies. I am currently an

elected member of the Management Committee of the

New Zealand Geotechnical Society, and hold the role of Vice-

Chair.

2.3 I have 30 years‟ experience in geotechnical and civil

engineering, and over the past 26 years I have provided

geotechnical advice on a wide variety of civil, commercial,

industrial, and land development projects in many parts of

New Zealand, and in Australia and further afield.

2.4 Projects I have provided advice on include the Tauranga

Eastern Link highway (TEL), the Ngaruawahia Section of the

Waikato Expressway (Ngaruawahia), and the recent Board of

Inquiry hearing on the Waterview Connection Project

(Waterview).

2.5 The TEL project comprises a new four lane highway some

23 km in length with seven bridges and some three million

cubic metres of earthworks. I was the lead geotechnical

engineer for the early stages of that project, and reviewed

the geotechnical work of my colleagues as it developed and

was consented. TEL is currently being designed and built by a

consortium of constructors and designers, and I continue to

review the work of my colleagues as they fulfil Beca‟s role as

advisor to the NZ Transport Agency (NZTA). From a

geotechnical perspective, it has many similarities to the

Mackays to Peka Peka Expressway (the Project), in that it

requires the construction of a multi-lane highway through

sand dunes and over peat lands, and involves the careful

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consideration of ground settlement, liquefaction potential and

the seismic performance of relatively high embankments at

bridges.

2.6 The Ngaruawahia project comprises 12 km of new four lane

expressway, with six bridges and some 1.2 million cubic

metres of earthworks, and is located in the northern Waikato.

It is currently being constructed by a design-build team, with

Beca providing geotechnical design. I am the geotechnical

reviewer for that project. It includes the construction of a

multi-lane highway over peat lands and, as for TEL, involves

the careful consideration of ground settlement, liquefaction

potential and the seismic performance of relatively high

embankments at bridges.

2.7 Both of these projects are, therefore, directly relevant to the

Mackays to Peka Peka Project.

2.8 My role on Waterview was focussed on the ground settlement

effects from tunnel and retaining wall construction. It involved

the estimation of the quantum of ground settlement resulting

from the project and assessment of the effects of that

settlement on houses, other structures and buried and

surface infrastructure. I have adopted the same assessment

methodologies used on Waterview for the current Project.

2.9 I led the drafting of the proposed settlement effects

management plan and the ground settlement conditions for

Waterview, and participated in expert conferencing to develop

an agreed set of conditions for consideration by the Board of

Inquiry (BOI).

2.10 I am currently the reviewer for ground settlement related

assessments and monitoring for the Well Connected Alliance

which is designing and constructing the Waterview Connection

project.

3 My evidence is given in support of the Notice of Requirement (NoR)

and applications for resource consent lodged with the Environmental

Protection Authority (EPA) by the NZTA for the construction,

maintenance and operation of the Project.

4 I am familiar with the area that the Project covers and the State

Highway and local roading network in the vicinity of the Project.

5 I have directed and reviewed all geotechnical aspects of the design

and the ground settlement effects assessment for this Project since

mid-2010. In the course of my involvement, I have worked closely

with my colleagues, particularly Ms Ann Williams, who has

undertaken groundwater modelling.

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6 I am the reviewer of the Assessment of Ground Settlement Effects

Technical Report and of the Geotechnical Interpretive Report1 which

form part of the Assessment of Environmental Effects (AEE) lodged

in support of the Project.

7 My evidence covers the assessment of potential ground settlement

associated with the construction and operation of the Project, and

the potential effects of these settlements on existing buildings,

services and infrastructure. It describes the monitoring regime

proposed, together with potential mitigation measures for ground

settlement effects (if any).

8 I have read the Code of Conduct for Expert Witnesses as contained

in the Environment Court Consolidated Practice Note (2011), and I

agree to comply with it as if this Inquiry were before the

Environment Court. My qualifications as an expert are set out

above. I confirm that the issues addressed in this brief of evidence

are within my area of expertise. I have not omitted to consider

material facts known to me that might alter or detract from the

opinions expressed.

SCOPE OF EVIDENCE2

9 My evidence will deal with the following:

9.1 Executive summary;

9.2 Background and role;

9.3 A brief description of the existing ground conditions (which

are discussed more fully in the evidence of Ms Ann Williams);

9.4 Assessment of ground settlement effects;

9.5 Response to submissions;

9.6 Response to the BOI‟s section 92 request;

9.7 Proposed conditions; and

9.8 Conclusions.

1 Technical Reports 35 and 36 respectively.

2 I have reviewed the section 149G Key Issues Reports prepared by Greater

Wellington Regional Council and Kãpiti Coast District Council. There are no

issues raised that relate to ground settlement or that otherwise require a response from me.

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EXECUTIVE SUMMARY

10 My evidence addresses the potential ground settlement effects

resulting from construction and operation of the proposed

Expressway. It also discusses the general ground conditions and

key geotechnical considerations that have been identified for the

proposed Expressway.

11 There are four predicted sources of settlement associated with

construction and operation of the Expressway, of which the first two

listed below are by far the most significant:

11.1 Ground consolidation due to the construction of road

embankments. This consolidation occurs beneath and for a

small distance beyond the embankments where they are

constructed on peat.

11.2 Ground consolidation due to lowering of the groundwater as a

result of excavation. This is also confined to peat soils. It is

time dependant and will extend for a greater distance beyond

the earthworks footprint. Permanent lowering of the

groundwater level in peat may also result in drying induced

volume change settlement.

11.3 Mechanical settlement of the ground due to movement of

retaining walls. This is much more localised and of

considerably smaller magnitude than consolidation

settlement.

11.4 Mechanical settlement of the ground due to vibration. This is

expected to only result from construction activities which are

intended to densify the adjacent soil. It is, therefore,

extremely localised and the effects are built out by

subsequent construction.

12 Field and laboratory investigations have been carried out to

characterise the soils at the Project site. These investigations have

included a trial embankment to investigate the settlement behaviour

of the peat soils that underly a significant portion of the site and in

which the most significant settlement is expected to occur.

13 Numerical analysis of settlement has been undertaken for each of

the potential sources identified, and these have been combined

where appropriate to determine total settlement contours. The

largest component of settlement results from embankment loading

and as a result has little effect on surrounding properties or

infrastructure. Settlement arising from groundwater drawdown in

peat soils is more extensive, but the magnitude is typically small

because of the limited groundwater change expected.

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14 The effects on buildings have been assessed following the approach

that was adopted for the Waterview Connection project. Applying

this approach, the assessment concluded that there will be

negligible setlement effects on all buildings from the construction

and operation of the Expressway. Similarly low effects are predicted

on buried services that are not proposed to be relocated as part of

the project, and on rail infrastructure. Road surfaces that are

affected by the Project will be remediated by resurfacing.

15 Monitoring is proposed to confirm the predicted settlement and the

predicted effect of that settlement. While the current assessment

indicates that mitigation of settlement effects is not required, there

are mitigation measures that can be implemented if required. These

include changing the construction methodology in areas of peat to

reduce the extent of dewatering, and the installation of groundwater

recharge trenches.3

16 I have reviewed submissions lodged on the Project relevant to my

area of expertise. Nothing raised in those submissions causes me to

depart from the conclusions reached in my technical assessment of

the Project.

BACKGROUND AND ROLE

17 The NZTA selected an alliance comprising Fletcher Construction,

Higgins Group, and Beca Infrastructure, together with several

support organisations (the Alliance) in mid-2010 to design and

construct the Project.

18 I have directed and reviewed all geotechnical aspects of the Project

since the inception of the Alliance. That has included participation in

workshops to develop the initial concepts, contribution to the multi-

criteria analysis of the various options, and direct discussion with

inter-related disciplines, in particular with Ms Ann Williams on

groundwater and Mr James Whitlock on vibration.

19 A team of engineers and engineering geologists from Beca

undertook the current geotechnical investigations and prepared the

Geotechnical Interpretive Report (Technical Report 36) and the

Assessment of Ground Settlement Effects (Technical Report 35).

That team consisted of:

19.1 Ms Lucy Coe – Associate, Geotechnical Engineering;

19.2 Ms Jennifer Bradshaw – Engineering Geologist;

19.3 Mr Aidan Thorp – Geotechnical Engineer; and

3 Further examples are provided in Technical Report 35, Section 7.2.

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19.4 Mr Jamil Khan – Associate, Structural Engineering.

20 My role was to guide development of the assessment methodology

and to peer review the Technical Reports.

21 Assessment of ground settlement requires consideration of the

magnitude of ground movements resulting from groundwater

changes and from the direct loading of compressible soils (known as

consolidation settlement) and of movement resulting directly from

excavation (known as mechanical settlement).

22 For this Project, the settlement of by far the greatest magnitude

(and hence interest) arise from the preloading of peat4 (by the

proposed embankments) and from long term groundwater lowering

within adjoining peat lands resulting from permanent excavation,

typically for some of the proposed stormwater wetlands and offset

flood storage areas. The settlement occurs predominantly within the

underlying and surrounding peat. Settlement within the underlying

sand is much (typically several orders of magnitude) less than that

occuring within the peat, so has not been separately considered.

23 Embankment loading related settlement is largely confined to the

land beneath and extending a short distance away from the fill area.

As a result, it has little effect on adjoining property or services. It is

only an issue when considering earthworks volumes.

24 Groundwater lowering of peat by the formation of permanent ponds

or offset storage areas with outlets below the existing groundwater

level results in more widespread effects, albeit of smaller magnitude

than the settlement arising from embankment loading.

Consequently, the Assessment of Groundwater Effects Report

(Technical Report 21) is of fundamental importance to the

assessment of settlement. My team has used the groundwater

changes from that report (as discussed in the evidence of Ms Ann

Williams) to calculate consolidation settlement resulting from

groundwater lowering.

25 Ground settlement effects comprise not just the amount of surface

movement but, more importantly, the effects of that movement on

buildings and infrastructure. Those assessments were made by my

civil and structural engineering colleagues at Beca and on the

Alliance and have been reviewed by me.

4 Peat typically comprises unconsolidated black or dark brown soil consisting

largely of slightly decomposed or undecomposed vegetable matter that has accumulated in a waterlogged environment. The level of decomposition varies

along the Project site. For the purpose of this assessment, fully decomposed

(termed amorphous) peat and organic rich sandy soils have also been treated as peat.

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26 The Assessment of Ground Settlement Effects Report which

addresses each of these issues was lodged with the EPA on 20 April

2012 as part of the overall AEE (specifically, Volume 2 Chapter 26,

and Volume 3, Technical Report 35).

27 The proposed approach for monitoring and, if required, mitigation of

settlement effects associated with the Project is included in Section

7 of that Report. This has informed the Settlement Effects

Management Plan (SEMP) (contained in Construction Environmental

Management Plan (CEMP) Appendix J, Volume 4), which describes

the proposed settlement monitoring and mitigation measures in

detail.

28 Technical Report 35 was informed by, and relies upon other

technical reports lodged with the EPA in support of the Project,

those reports being primarily:

28.1 Assessment of Groundwater Effects (Technical Report 21);

and

28.2 Geotechnical Interpretive Report (Technical Report 36).

GROUND CONDITIONS

29 An assessment of the geotechnical and geological conditions for the

Project is presented in Technical Report 36, the Geotechnical

Interpretive Report, and forms part of the Assessment of

Environmental Effects Report. Technical Report 36 is based on the

results of earlier geotechnical investigations by others and on more

recent investigations carried out by the Project team in 2010 and

2011. The extent and location of all investigation work is shown on

plans contained in Technical Report 36.5

30 A description of the existing geology is provided by Ms Ann

Williams in her evidence and hence this section of my evidence

presents a summary of the relevant geotechnical aspects of the

Project.6

31 The proposed Expressway corridor traverses sand dunes, swamp

deposits, and alluvium, underlain by a thick sequence of older

marine and alluvial sand and gravel deposits, with greywacke

bedrock at depth.

5 Appendix 36.A of Technical Report 36.

6 This is further detailed in Section 3 (Existing environment) of Technical Report 35.

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32 The key geotechnical considerations that have been identified for

the proposed Expressway are:

32.1 The presence of peat deposits across the site, and associated

embankment settlements and stability;

32.2 The high seismic hazard and known active faults;

32.3 The presence of relatively loose to medium dense saturated

sand deposits with the potential to liquefy during moderate to

significant design seismic events;

32.4 The potential for liquefaction induced slope instability and

settlement; and

32.5 Founding conditions for bridge structures comprising alluvial

deposits to depth, predominately interbedded dense sands

and gravels.

33 These considerations have been responded to and are reflected in

the Project‟s scheme design (through avoidance and mitigation).

34 Peat deposits are present along the route in the low lying inter-

dunal depressions. The peat is very soft, with a high water content

and compressibility. These deposits are typically 0.5 m to 4.0 m

thick, but are up to 6m thick in some locations.

35 The presence of peat deposits presents constraints to the design of

embankments due to the relatively large and ongoing settlement

that occurs when these soils are loaded. Such settlement can affect

the smoothness of the road surface and cause rainwater to pond, as

well as affecting underlying and adjacent services and adjacent

structures and properties.

36 Groundwater level lowering in peat deposits can also lead to ground

surface settlement. These groundwater changes, and the resulting

settlement, can extend some distance beyond the footprint of the

Project.

37 The relatively weak peat deposits can also affect the stability of

higher embankments, in particular during the construction stage

and during or following a seismic event.

38 The alignment is located in an area of high seismicity and the

Alliance has completed a site-specific seismic hazard assessment to

refine the seismic hazard.7 My analyses indicate that, where

saturated, the loose to medium dense sands present on the site are

susceptible to liquefaction during a moderate or significant

7 Technical Report 36, Section 3.6.

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earthquake event. Liquefaction is expected to result in settlement,

slope instability and horizontal movements of dunes and

embankments.8

ASSESSMENT OF GROUND SETTLEMENT EFFECTS

39 In this section of my evidence, I will briefly describe the key points

of Technical Report 35.

40 The Report presents the results of the assessment of potential

ground settlement associated with the construction and operation of

the proposed Expressway, and the expected effects of that

settlement on existing buildings, services and transport

infrastructure.9

41 In the Report, the sources of settlement are detailed and the

magnitude of settlement calculated to assess the settlement effects

including the effects on buildings, services and infrastructure.10 A

monitoring regime and potential mitigation measures are also

provided in the Report.11

42 The Report, and the accompanying SEMP, focuses predominantly on

the damage potential arising from settlement (i.e. the effects),

rather than the quantum of settlement itself.

Sources of settlement effects

43 There are four predicted sources of settlement associated with the

construction and operation of the proposed Expressway, as

described below:

44 Consolidation of the ground due to the construction of

embankments.12 Such settlement occurs beneath and for a small

distance beyond the embankments where they are constructed on

peat. As a result, it primarily affects the completed highway

pavement, roadside drainage and furniture, and any services buried

within the underlying peat. Consolidation settlement is time

dependent and is directly related to the embankment height and to

the nature, thickness and permeability of the peat. Most of this

movement will occur during construction, with ongoing secondary

compression (creep) settlement continuing at a reducing rate

through operation. The magnitude and rate of this settlement

greatly affects construction planning and earthworks volumes, but


9 Technical Report 35, Sections 5 and 6.

10 Technical Report 35, Section 5.

11 Technical Report 35, Section 7.


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has little effect on buildings and infrastructure beyond the Project

footprint due to its localised extent.

45 Consolidation of the ground due to lowering of the groundwater:13

Lowering of the groundwater level will occur as a result of

excavation, which may be either temporary (e.g. short term

undercutting to remove peat from beneath the embankment

footprint or in other areas) or long term around some of the

excavated stormwater wetlands and offset flood storage areas.

Consolidation settlement is time dependent, and will extend beyond

the earthworks footprint. Consequently, it has the potential to affect

buildings and infrastructure beyond the Project footprint, particularly

where the groundwater changes are essentially permanent.

46 Permanent lowering of the groundwater level will potentially result

in drying induced volume change settlement. The change in

moisture content is expected to be relatively small as a result of

infiltration recharge. The groundwater drawdown beyond the Project

footprint is modest, and complete drying is not expected to occur.

Consequently, the drying induced volume change is expected to be

relatively small in comparison with the settlements resulting from

consolidation due to the groundwater lowering.

47 There is one potential exception to this, around Offset Flood Storage

Area 2, where permanent groundwater lowering is proposed and

more extensive drawdown has been predicted.14 I will return to this

later in my evidence.

48 I acknowledge that there are uncertainties involved in the prediction

of settlement of peat and other organic rich soils. Many of these

have been identified in the BOI‟s section 92 request,15 which I

respond to below. I accept that it is not practical to precisely define

the distribution of likely ground settlement resulting from the

Project. As a result, in my assessment, I have adopted a

conservative approach to assessing the extent and quantum of

settlement that is likely to occur, and have based my assessment of

the resulting effects on buildings and infrastructure on that

conservative assessment.

49 Consequently, I consider that my assessment presents an upper

bound to the likely ground settlement effects of the Project.

Monitoring of settlement and of effects on buildings and

infrastructure will be used to confirm the effects are no worse than

this assessment, and mitigation measures are available in the event

that the effects are greater than has been predicted.


14 Technical Report 21, Figure F8b.

15 Section 92 request dated 9 August 2012.

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50 Mechanical settlement of the ground due to the movement of

retaining walls:16 Lateral movement of embedded retaining walls (as

the ground is excavated in front of them) results in localised

settlement of the ground above. These settlements occur relatively

quickly, during and immediately following wall construction. I expect

them to be of small magnitude and of localised extent when

compared to the settlement resulting from embankment loading.

51 Mechanical settlement of the ground due to vibration17: Vibration is

used in construction to densify sandy or gravelly soils. This

densification results in immediate settlement of the ground surface

extremely close to the vibration source. Vibration resulting from

general construction operations, and from traffic on the completed

Expressway, is not expected to generate sufficiently high shear

stresses to cause ground settlement. Consequently, vibration

induced settlement is confined to the construction footprint and is

essentially “built out” by the construction operation.

Methodology of calculating settlement effects

52 The methods used for calculating settlement and assessing the

subsequent effects are detailed in Section 4 (Methodology) of

Technical Report 35.

53 The extent of ground settlement resulting from the Project has been

determined by combining, as applicable, the settlement caused by

the various sources described above. Plans showing the area of

expected effects are provided in Appendix 35.G to Technical

Report 35 and are attached to my evidence as Annexure A.

54 The consolidation settlement from the two primary sources (new

road embankment and groundwater lowering) have been analysed

separately, at a number of cross-sections along the length of the

proposed Expressway.18 The same cross-sections have been used

for each set of analyses. The settlement profiles have then been

combined to assess the total predicted consolidation settlement. The

cross-sections have been selected to be representative of the

varying peat thicknesses and peat treatment methodologies for the

new road embankment. In addition, the cross-sections cover the

new stormwater wetlands and offset flood storage areas that may

result in lowering of the groundwater level.19

55 Mechanical settlements will occur as a result of construction of the

new retaining walls and from construction vibrations. These

settlements are significantly smaller, in both magnitude and extent,



18 The embankment and groundwater drawdown settlement methodologies are

presented respectively in Sections 4.3 and 4.4 of Technical Report 35.

19 As identified in Technical Report 21, Volume 3.

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than the consolidation settlements. They have been considered

independently and then incorporated into the total settlement

assessment as applicable.20

56 The groundwater consolidation settlement is based on worst case

drawdowns, conservatively ignoring time effects and the likelihood

of recharge before temporary drawdown resulting from peat

undercut and backfill (which will occur on the same day in any

particular area of embankment construction) has time to fully

develop. Mechanical settlement develops almost immediately as

construction proceeds. As a result, it has a single critical stage,

which is the long term.

57 The effects on buildings were assessed using an internationally

accepted method.21 This method was also used to assess the effects

for the Waterview Connection project in Auckland, and remains the

most commonly used and recommended method in international

references. The method determines the curvature and horizontal

strain in a building and plots these values against criteria to assess

the likely effect on a structure. The classification of potential effects

(Damage Category) is then determined. The method has been

derived for unreinforced masonry buildings, so can be considered

conservative for timber framed and reinforced concrete buildings.22

58 The assessment considered a “generic” residential building and also

looked at 15 specific commercial and industrial buildings that were

identified as being close to the potential area of settlement, as well

as the KCDC Waste Water Treatment Plant and the Waikanae

Christian Holiday Camp („El Rancho‟).

59 The effects on local services and transport infrastructure were

assessed by calculating the predicted change in their gradient as a

result of any differential settlement and then determining whether

that change can be tolerated by each item being assessed.23

Settlement Estimates and Effects

60 The consolidation settlement arising from construction of the new

road embankment governs the settlement below the proposed

Expressway footprint. The predicted settlement away from the

proposed Expressway is predominately from groundwater drawdown

settlement due to construction of those stormwater ponds, wetlands

20 The method for assessing the new retaining wall settlements and the vibration

assessment of settlements are presented in Sections 4.5 and 4.6 respectively of Technical Report 35.

21 Burland, J.B. (1997), “Assessment of risk of damage to buildings due to tunnelling and excavation”, Earthquake Geotechnical Engineering, Ishihara (ed),

Balkema, Rotterdam.

22 This is discussed in Section 4.8.1 of Technical Report 35.

23 This is discussed in Sections 4.8.2 and 4.8.3 of Technical Report 35.

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and offset flood storage areas alongside the proposed Expressway

which result in groundwater lowering. Within the 10m immediately

adjacent to the proposed Expressway footprint, settlement results

from a combination of these two sources.24

61 Plans showing the extent and magnitude of expected settlement are

provided in Appendix 35.G to Technical Report 35 (and attached as

Annexure A to my evidence).

62 The effects assessment predicts that there will be negligible effects

on all buildings from the construction and operation of the

Expressway. The predicted damage from this category is defined as

no more than “hairline cracks” less than 0.1mm wide.25

63 This classification includes the specifically assessed commercial and

industrial buildings, Kāpiti Coast District Council Waste Water

Treatment Plant and the Waikanae Christian Holiday Camp. I note

that there is no predicted settlement arising from the Project within

the extent of the Camp.26

64 The assessment predicts negligible settlement effects on those

services not proposed to be relocated.27

65 Where the proposed Expressway crosses existing roads, the physical

construction works will include modification and re-surfacing of the

local road at those crossings. The settlement effects will be

remediated as part of the resurfacing of these roads. The effects on

rail infrastructure are assessed to be low, and any re-levelling, if

required, will be agreed with KiwiRail.28

66 Construction of Offset Flood Storage Area 2 is expected to result in

groundwater lowering for some distance beyond the Project

footprint, as noted earlier in my evidence. Groundwater lowering of

0.6m has been modelled in the immediate vicinity of this wetland.29

The resulting settlements have been calculated based on a

groundwater level at 0.5m depth below the ground surface. Eight

hand auger bores have been put down in the potentially affected

area as part of a recent stage of geotechnical investigations, which

followed completion of Technical Report 35. Those bores indicated a

lesser plan extent of peat than had been assumed in our

assessments. They also identified late autumn (May) groundwater

24 This can be seen on cross sections showing total settlements and the two

component parts presented in Appendix F of Technical Report 35.

25 Technical Report 35, Section 4.8.1, Table 10.

26 Technical Report 35, Sections 6.2.2 to 6.2.5.



29 Technical Report 21, Figure F8b, and Section 5.2.4 of Technical Report 35.

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levels at between 1.2m and 1.4m depth below the ground surface.

The groundwater model was calibrated to an average groundwater

level close to the surface beneath Rata Road.30 Consequently, the

predicted groundwater drawdown remains within the current

seasonal range, and additional drying related settlement is not

expected. As a result, I expect that groundwater lowering will not

extend as far beyond the Project as has been modelled,31 and that it

will not produce additional drying induced volume change

settlement.

Monitoring

67 Monitoring of actual ground settlements and the resulting effects will

be undertaken to confirm the estimated settlements and the

predicted effects of those settlements. The proposed monitoring is

described in detail in Technical Report 35 and the SEMP.32 It

comprises vertical monitoring of survey marks, condition

assessments of specified buildings and specific monitoring of

retaining walls and services.

68 Monitoring of groundwater levels and their changes can provide an

early warning of potential consolidation settlements. Groundwater

monitoring thus forms part of the overall settlement mitigation

monitoring strategy proposed for the Project.33

69 The frequency of monitoring will depend on the vulnerability of the

object being monitored and its proximity to the active construction

area, the stage of construction and the results of previous

monitoring.

Mitigation and remediation

70 The current assessment indicates that mitigation is not required

from settlement effects. However, Technical Report 35 does present

mitigation measures available that could be implemented to cover

the unlikely scenario of greater than predicted damage occurring.34

71 The Report sets out contingency measures for road embankment

settlement, groundwater drawdown settlement, and retaining wall

settlement. Building mitigation available includes repair of any non-

structural defects once settlement is substantially complete (ie when

the rate of movement is sufficiently low that repair is worthwhile)

and the immediate repair of any issues that are structural or will

affect the weather tightness of a building.

30 Technical Report 21, Section F3.2.


32 Section 7 of Technical Report 35, and Section 3.2 of the SEMP (see CEMP,

Appendix J, Volume 4).

33 Refer Groundwater (Level) Management Plan (CEMP, Appendix I, Volume 4).

34 Section 7.2 of Technical Report 35.

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72 Services mitigation available depends on the type of service and its

construction, but includes temporary or permanent diversion, repair

or replacement. Road and rail could be remediated, if necessary, by

relatively minor surface reconstruction methods.

RESPONSE TO SUBMISSIONS

73 I have read all of the submissions lodged on the Project that raise

ground settlement or issues relevant to my expertise in geotechnical

engineering. Submitters have raised a number of ground settlement

concerns. A larger number of submitters identify the potential

challenges that the peat and sand at the site pose for earthworks,

performance during earthquakes, and liquefaction potential. In this

section of my evidence, I will firstly address the submissions that

are directly related to ground settlement effects. I will then turn to

the broader geotechnical concerns that have been raised.

74 Neither the Greater Wellington Regional Council nor the Kāpiti Coast

District Council has raised concerns or issues in their respective

submissions in relation to ground settlement or other geotechnical

matters. Accordingly, I do not refer to their submissions here.

Ground settlement issues

75 D and D Waterson, 16 Rata Rd, Raumati35 – express concerns that

they may begin experiencing problems with their property including

the foundations of their house as a result of nearby peat removal,

filling and groundwater changes. The estimated settlements

resulting in this area are shown in Technical Report 3536 and on

Sheet 3 of Annexure A. This property is located well beyond the

Project footprint, and beyond the modelled extent of measurable

groundwater drawdown.37 Consequently, it is not expected to

experience settlement resulting from fill loading or groundwater

changes.

76 B Harrison, 106 Leinster Ave, Raumati South38 – expresses concerns

regarding land subsidence due to the water table being changed, as

well as potential damage to his house. The potential for such

subsidence, and the expected distribution of the resulting ground

settlement effects, is addressed in Technical Report 35. The

estimated settlements resulting in this area are shown in Technical

Report 3539 and on Sheet 2 of Annexure A. This property is located

beyond the Project footprint, and beyond the extent of measurable

groundwater drawdown. Consequently it is not expected to

35 Submitter 26.

36 Appendix G, Sheet 3 of 11.


38 Submitter 323.

39 Appendix G, Sheet 2 of 11.

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experience settlement resulting from fill loading or groundwater

changes.

77 A Laing, 169B Te Moana Rd, Waikanae40 – expresses concerns that

increased stormwater runoff will exacerbate subsidence on her

property that is underlain by peat deposits. It is not appropriate for

me to comment on the potential for stormwater runoff from the

Project affecting this property. I would, however, expect subsidence

to result from groundwater lowering rather than raising, and for

increased runoff to raise rather than lower groundwater levels.

Consequently, this concern is, in my opinion, unwarranted.

78 R Mackay, 14 Gavin Rd, Raumati Beach41 – states that settlement

may have a negative impact on homes near the Expressway. This

concern is the reason that considerable effort has been put into

modelling the ground settlement effects, as summarised in

Technical Report 35. As I state in paragraph 62 above, my effects

assessment predicts that there will be negligible effects on all

buildings from the construction and operation of the Expressway.

79 Paraparaumu/Raumati Community Board42 – identifies the potential

for adverse effects on ground stability of properties west of Rata

Road as a result of earthworks for Offset Flood Storage Area 2. The

Community Board requests continuous monitoring of groundwater

levels in this area before, during, and for 3 years after construction.

Ground settlement in this area has been specifically assessed43 and

is predicted to be less than 12.5mm. I have discussed the potential

for drying induced settlement in paragraph 66 above. Consequently,

I do not expect adverse ground stability effects to occur as a result

of the Project earthworks in this area. While monitoring of

groundwater changes is an important part of managing settlement

effects, as I discuss in paragraph 68 above, changes are progressive

and gradual, so in my view continuous monitoring is not warranted.

I expect periodic water level monitoring, as has been proposed by

Ms Williams, to be adequate to provide advance warning of

potential ground settlement.

80 Save Kãpiti Inc44 – identifies that the proposal will result in

drawdown of groundwater level and cause ground settlement over

an area extending well beyond the footprint of the designation. It

also identifies considerable uncertainty over the magnitude of

settlements and consequent adverse effects. While I share this

view, I consider that the settlement effects have been

40 Submitter 337.

41 Submitter 404.

42 Submitter 501.

43 Technical Report 35, Section 5.2.4.

44 Submitter 505.

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comprehensively modelled, as summarised in Technical Reports 21

and 35. The residual uncertainty is managed by the proposed

ground settlement and building condition monitoring programme,

which is described in the proposed Ground Settlement Conditions in

Annexure B.

81 Highway Occupants Group45 – identifies the absence of geotechnical

testing undertaken between chainage 3000 and 3700, immediately

north of Leinster Avenue, and suggests that this lack of technical

information undermines the assessment of effects. I do not agree.

The ground settlement effects have been assessed based on

contours of peat thickness46 derived from nearby subsurface data

and interpretation of the surface topography. Six hand auger bores

have been put down along this portion of the alignment as part of a

recent stage of geotechnical investigations, which followed

completion of Technical Report 35. Those investigations have

identified peat thicknesses close to (within 0.5m) the values used

for the assessment.47 I consider that the difference in ground

settlement effects will be small and that the current assessment

remains reasonable at this stage.

Building on sand and peat

82 Many submitters refer to the building of this Project on sand and

peat as carrying great risks and being expensive.48 I have discussed

these issues earlier in my evidence (paragraphs 32 to 37 above). I

can confirm that these issues have been carefully assessed and

quantified in the course of the geotechnical investigations and

design for the Project, and are, in my view, appropriately reflected

in the designs that have been developed to date and which form the

basis of the assessments of effects.

Earthquakes and liquefaction

83 Many submitters draw attention to the high earthquake hazard in

this part of New Zealand, to the high groundwater level, and to the

consequent potential for liquefaction of loose sandy soils.49 I note

45 Submitter 542.

46 Technical Report 35, Appendix B.

47 Namely the contours of peat thickness in Technical Report 35 Appendix B Sheets 2 and 3, which cover this area.

48 Submitters include C & M Dearden (261), D & D Waterson (267), Religious Society of Friends (330), C & I Baxter (422), B & J Inge (429), S Madden (459),

R. Love (470), Smart Transport Network (484), G Allen (523), L Allen (524), J Short & G Schwass (531), M Ellis (534), S Arnold (567), D Connal (616), D & S

Simmons (648), J Nisbet (649), D Peters (693), and J Svendsen (733).

49 Submitters include D Hawken (072), K Hare (150), T & A Davies (184), B

Tennyson (191), L Taylor (210), C & M Dearden (261), D & D Waterson (267), R Marshall (279), M Burton (299), L Pomare (309), Religious Society of Friends

(330), H Hopkirk (336), J Downie (346), C Keno (357), C & I Baxter (422), B & J Inge (429), S Madden (459), K Pomare (465), W & D Lattey (466), R. Love

(470), Smart Transport Network (484), D Kieboom (494), K Allan (502), S

Edbrooke (517), G Allen (523), L Allen (524), J Short & G Schwass (531), M Ellis (534), S Arnold (567), R Starke (589), S Heppenstall (598), K Nauta & D Jones

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that these issues have been previously identified and discussed in

the Geotechnical Interpretive Report,50 and I have discussed them in

paragraphs 32, 33 and 38 above. I can confirm that these issues

have been carefully assessed and quantified in the course of the

geotechnical investigations and design development, and are, in my

view, appropriately reflected in the designs that have been

developed and which form the basis of the assessments of effects.

The seismic design standards for this Project are considerably higher

than would commonly be adopted for a new building, and result in

extensive mitigation of the liquefaction risk in the vicinity of new

structures and specific measures to limit earthquake induced

displacement of the higher embankments.

RESPONSE TO THE BOI’S SECTION 92 REQUEST

84 I have reviewed the section 92 RMA request made by the BOI (by

letter dated 7 August 2012) and in this section of my evidence I will

address matters identified in Appendix One relating to peat

settlement. I have reproduced the matters raised and respond to

each item in turn below.

85 The request asks for further comment on the following items in

relation to ground settlement effects:

85.1 The assessment of peat properties and the subsequent

effects of ground settlement. Including the long term

effects of loading and dewatering to confirm

predictions used. The derivation of peat properties is

described in the Geotechnical Interpretive Report.51 Those

properties have been developed from field and laboratory test

results from historic and current geotechnical investigations in

the area, along with interpretation of field trials and

construction records.52 These parameters have been used to

calculate settlement resulting from embankment loading and

due to groundwater drawdown (dewatering), as has been

presented in the Assessment of Ground Settlement Effects53

and as I have summarised above. As I have stated in

paragraphs 48 and 49 above, there are many uncertainties

involved in the prediction of settlement on peat. As a result, I

have made a conservative assessment, and have proposed a

(600), D Connal (616), A Cherrill (630), D & S Simmons (648), A Soncodi (652),

N Beechey (663), E Hinkley (673), M O‟Sullivan (675), R & M Starke (690), D Peters (693), M & J Harris (713), R Snyders (720), S Woods (723), and J

Svendsen (733).

50 Technical Report 36 at Sections 3.4 to 3.7, and Section 5.2.


52 As identified in Table 5, p.20, Technical Report 36.

53 Technical Report 35.

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monitoring programme54 to confirm the predictions and that

the effects are no worse than has been assessed.

85.2 Possible further mechanisms that led to settlement of

peat or the timeframes under which ongoing

settlement may take place. In particular:

(a) The susceptibility of organic matter in the peat to

biological oxidation. Oxidation is recognised as one

of the components of peat land subsidence resulting

from drainage.55 While I am not aware of any studies in

New Zealand, subsidence resulting from oxidation of

peat has been found in the Netherlands to contribute

around 50% of the total subsidence arising from

drainage.56 As I have discussed in paragraph 66 above,

extensive permanent groundwater drainage modelled

to result from the Project is largely confined to the area

around Offset Flood Storage Area 2. The predicted

groundwater drawdown at this location remains within

the current seasonal range, and oxidation and

additional drying related settlement is not expected.

(b) Likely proportion of shrinkage induced volume

change on changing water contents. This aspect

has not been specifically studied, as groundwater

changes beyond the Project are limited in extent, and

the moisture content of the peat is expected to remain

high as a result of infiltration recharge.57

(c) Design parameters for secondary consolidation.

The trial embankment constructed as part of this

Project continues to be monitored and will ultimately

provide useful data on secondary consolidation.

Monitoring and analysis for the nearby Mackays

Crossing Project58 indicates secondary consolidation of

peat over a 10 year period to comprise around 10% of

the total settlement arising from the highest part of

that embankment. As a result, secondary consolidation

54 Paragraphs 67 to 69 above.

55 With the others being shrinkage due to withdrawal of moisture from surface layers by evapotranspiration, and consolidation/compression (as I have assessed

in Technical Report 35), refer Schothorst, C.J. 1977. Subsidence of low moor peat soils in the Western Netherlands. Institute for Land and Water Management

Research, Wageningen. Technical Bulletin No. 102, referenced in Andriesse, J.P. (1988), Nature and management of tropical peat soils, FAO Soils Bulletin 59.

56 Andriesse, J.P. (1988), Nature and management of tropical peat soils, FAO Soils Bulletin 59

57 Technical Report 35, Section 4.4.3 and Technical Report 36, Section 6.3.

58 Palmer, S.J. (2010), An embankment on peat. Mackays crossing road over rail bridge, Wellington, NZ, in Geologically Active, Taylor and Francis Group, London

21

042590992/2258990.8

has not been separately assessed at this stage.59 It is

considered to lie within the accuracy of the current

settlement assessments.

(d) Proportion of peat with Cv higher or lower than

the adopted typical proposed value. Fifteen

consolidation tests have been carried out on samples of

peat. From these, the Coefficient of Consolidation, Cv,

over a low stress range representative of groundwater

drawdown effects ranges from 0.75 to 62 m2/yr.

Neglecting the largest value (to avoid a single large

value skewing the data), the numerical average Cv

from these samples is 9 m2/yr. The coefficient of

consolidation has also been derived from the

monitoring of two trial embankments, and a design

value of 3.0 m2/yr has been adopted.60 Three of the

test results (20%) are less than this design value over

a low stress range, and the remainder are higher. A

small Cv results in a longer time for consolidation, so it

follows that, in most cases, primary consolidation

settlement will occur more rapidly than has been

predicted.

(e) Drill hole logs and laboratory test data. Field

investigation locations are shown on plans contained in

the Geotechnical Interpretive Report.61 Subsurface and

laboratory test data has been obtained from a number

of sources, which are referenced in the Geotechnical

Interpretive Report.62 A Factual Geotechnical Report

has been prepared which contains the results of the

Phase 1 investigations undertaken specifically for this

Project.63 All of this data has been used to build up the

geotechnical model for the Project area, which forms

the basis of the assessment of effects.

(f) Spatial distribution of the various types/grades

of peat. The nature of the peat across the Project is

described in general in the Geotechnical Interpretive

Report.64 Contours of inferred peat thickness are

presented in that report.65 The degree of


60 Technical Report 36, Table 6.

61 Ibid, Appendix 36.A.

62 Ibid, Section 8.

63 M2PP-AEE-RPT-GT-GE-090 (2011): MacKays to Peka Peka Expressway Alliance:

Phase 1 Investigation – Factual Geotechnical Report.


65 Ibid, Appendix 36.B.

22

042590992/2258990.8

decomposition, from undecomposed fibrous peat to

completely decomposed amorphous peat, has been

assessed in the course of recent investigations using

the widely adopted methodology of von Post,66 and is

presented on the bore and pit logs.

(g) The secondary and tertiary (creep) consolidation

that will take place. As I have discussed under (c)

above, secondary consolidation is assessed to form

only a small component of settlement beyond the

Project, so has not been separately considered. I

expect these aspects of settlement of peat to be more

closely addressed in the course of detailed design, as

they have greater bearing on the design of the

embankments themselves to achieve particular long

term settlement performance.

(h) The annual rate of settlement and duration of

settlement. The trial embankment undertaken for this

Project provides useful field scale guidance on the rate

and duration of settlement that will occur as a result of

embankment loading. The trial suggests that the

majority of primary consolidation occurs relatively

quickly (within 1-2 months of completion of loading).

(i) The sensitivity of settlement predictions to

variations in the parameters adopted in the

analysis. The sensitivity of calculated settlement to

various input parameters has been checked in the

course of assessing the ground settlement effects.67

The analyses showed little sensitivity to the selected

parameters for peat thicknesses of up to 1.5m. At

greater peat thickness, the calculated settlement

becomes more sensitive to the pre-existing building

load, with heavier buildings proving more sensitive to

groundwater level changes than lighter ones.

PROPOSED CONDITIONS

86 In the documentation lodged with the AEE, the NZTA included a set

of Proposed Resource Consent Conditions.68 This included proposed

ground settlement conditions G.31 and E.12 to E.23 which are

attached to my evidence as Annexure B.

66 Farrell, E.R. (2012), Organics/peat soils, Chapter 35 of ICE Manual of

Geotechnical Engineering, Institution of Civil Engineers, Table 35.3.

67 Technical Report 35, Section 4.4.3.

68 AEE, Chapter 33.

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87 Condition G.31 requires a SEMP to be finalised and submitted for

certification before works commence.

88 A draft SEMP has been prepared and is included as Appendix J of

the Proposed CEMP. The purpose of the SEMP is to address potential

ground settlement associated with construction and operation of the

Expressway, and the effects of that settlement on existing buildings,

services and transport infrastructure. That draft will be updated,

finalised and certified by the GWRC before works commence.

89 The process for managing and mitigating settlement effects is set

out in the draft SEMP, and follows the following steps (items in

brackets refer to the relevant Proposed Conditions):

89.1 Identify susceptible buildings, services and other

infrastructure (E.17).

89.2 Estimate settlements and resulting effects, and establish

trigger levels, to form the basis of monitoring (Technical

Report 35, updated as required following BOI decision and

detailed design).

89.3 Establish current conditions by pre-construction monitoring

(E.12, E.13) and condition assessments (E.18, E.19, E.23).

89.4 Monitor (E.13, E.20, E.23) and report (E.16, E.22),

responding to any alerts (E.14).

89.5 Mitigate as required during construction, by modifying the

construction approach or by implementing interim repairs

(E.14, E.23).

89.6 Undertake a post construction condition assessment and

repair as required (E.21, E.23).

90 I consider that these Proposed Conditions set out an appropriate

process for addressing ground settlement effects.

CONCLUSIONS

91 The ground settlement effects arising from the Project are

predominantly seated in the underlying and adjacent peat soils.

They result directly from loading of those soils, and from

groundwater changes that may occur in them. Settlement arising

from groundwater changes is of greatest interest beyond the

immediate Project footprint.

92 The extent of peat beneath and adjacent to the Project has been

assessed using geotechnical data from the current and earlier

investigations in the area. Settlement parameters for the peat have

24

042590992/2258990.8

been derived from published data, from laboratory test results and

from the results of a trial embankment built for this project.

Groundwater changes have been adopted from the studies

undertaken by my colleagues as part of the Assessment of

Groundwater Effects.69

93 The settlement effects on buildings have been assessed and indicate

that there will be negligible settlement effects on all buildings from

the construction and operation of the Expressway. Similarly low

effects are predicted on buried services that are not proposed to be

relocated as part of the project, and on rail infrastructure. Road

pavements that are affected by the Project will be remediated by

resurfacing.

94 Monitoring is proposed to confirm the predicted settlement and the

predicted effect of that settlement. While the current assessment

indicates that mitigation of settlement effects is not required, there

are mitigation measures that can be implemented if necessary.

95 I therefore consider that the effects of the Project on ground

settlement will be no more than minor and can be effectively

managed by mitigation measures and consent conditions, should

monitoring indicate settlement that is greater than anticipated.

______________________

Gavin Alexander

3 September 2012

69 Technical Report 21.

25

042590992/2258990.8

ANNEXURE A: PREDICTED SETTLEMENT PLANS -

APPENDIX 35.G, TECHNICAL REPORT 35

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NZ TRANSPORT AGENCYWAt<A KOTAHI

Date

15.03.12NRNAmendment


OriginalScal@(A3)

NOTES:


26

042590992/2258990.8

ANNEXURE B: PROPOSED CONDITIONS

Settlement Management Plan

G.31 The consent holder shall finalise, submit and implement through the

CEMP, the Settlement Management Plan (SEMP) to be submitted to the

Manager for certification at least 15 working days prior to works

commencing. The purpose of the management plan is to address the

potential ground settlements (settlements) associated with construction

and operation of the Expressway, and the effects of these settlements on

existing buildings, services and transport infrastructure.

The SEMP shall include information regarding:

i. implementation and operational procedures;

ii. estimated total settlements

iii. monitoring methods;

iv. monitoring locations set out on a plan;

v. monitoring frequency;

vi. reporting requirements;

vii. alert and action programmes; and

viii. review procedures.

Settlement Conditions

E.12 The consent holder shall establish a series of ground settlement

monitoring marks to monitor potential settlement that might occur as

a result of construction of embankments and drawdown of the

groundwater table. The survey marks will be generally located as

follows:

a) 2 to 4 marks, established in cross-sections along the length of the

Expressway as set out in Appendix D of the SEMP (as required by

Condition G.31);

b) adjacent to stormwater features where groundwater drawdown of

more than 0.1 m has been predicted;

c) at the KCDC wastewater treatment plant; and

d) structures identified close to the Expressway where settlement of

more than 12.5 mm is predicted.

The locations of each type of settlement monitoring marks shall be

confirmed in the SEMP.

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E.13 The consent holder shall survey the settlement monitoring marks at

the following frequency:

a) Pre-construction - vertical at monthly intervals starting at least 12

months prior to construction commencing

b) During construction

i.vertical at 3 monthly intervals

ii.within 500 m of active construction – vertical at monthly

intervals

iii.within 50 m of excavation in front of retaining walls – vertical at

monthly intervals.

c) Post-construction

i.Vertical at 3 monthly intervals for 6 months

ii.Vertical at 6 monthly intervals for a further period of at least 2

years.

E.14 a) Immediately following each monitoring round, the consent holder

shall use the settlement monitoring results (together with the

results of groundwater monitoring where they may provide an

earlier indication of future settlements) to reassess the building

damage categories and compare them to those estimated in

Technical Report 35 - Assessment of Ground Settlement Effects, as

included in Condition G.1a) - b).

b) If the reassessment indicates that a building or structure has

increased its damage category, this shall be considered to be an

Alert Level and additional specific assessment of the structure shall

be carried out by the consent holder to confirm this reassessment

within 72 hours.

c) If the additional assessment confirms the increase in damage

category, this shall be considered an Action level and the owner

and occupier of the structure shall be notified within 72 hours.

d) Following consultation with the property owner and occupier,

subsequent actions may include increased frequency and/or extent

of monitoring, modification to the construction approach or

mitigation works to the affected structure.

E.15 The consent holder may reduce the frequency of settlement monitoring

required by Condition E.13:

a) Once the active construction stage has passed; and

b) 3-monthly monitoring has been carried out for a minimum of 6

months; and

c) The monitoring indicates that any potential settlement effects are

within a satisfactory range as specified in the SEMP; and

d) The criteria in E.15a)-c) has been certified by GWRC.

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E.16 The consent holder shall collate the results of the settlement

monitoring (undertaken pursuant to Conditions E.12-E.15) and prepare

a report that shall be made available to GWRC.

A settlement monitoring report shall be prepared:

a) prior to the commencement of construction; and

b) at 3-monthly intervals throughout the construction period; and

c) following completion of construction, a settlement monitoring

report shall be prepared following each round of settlement

monitoring undertaken (i.e. 3 monthly and then 6 monthly).

The purpose of the reports is to highlight any Alerts or Actions and

provide a full interpretation and/or explanation as to why these

occurred, the likely effects and any mitigation measures initiated as a

result.

E.17 The consent holder shall review and update the schedule of buildings

and structures considered to be at risk in accordance with the criteria

of the SEMP and maintain this schedule for review by GWRC. This

schedule shall include but not be limited to, the following properties:

a) KCDC wastewater treatment plant;

b) The Waikanae Christian Holiday Park (El Rancho); and

c) Specific buildings identified during the course of detailed design

where the total settlements are estimated to be greater than 25

mm.

E.18 The consent holder shall consult with owners of buildings and

structures identified in Condition E.17a)-c) and, subject to the owner’s

approval of terms acceptable to the consent holder, shall undertake a

pre-construction condition assessment of these structures in

accordance with the SEMP.

E.19 The consent holder shall employ a suitably qualified person to

undertake the building assessments required pursuant to Condition

E.18 and identify this person in the SEMP.

E.20 The consent holder shall undertake monthly visual inspections of the

following properties during active construction:

a) Dwellings where the total settlements are estimated to be greater

than 25 mm;

b) Dwellings where the predicted Building Damage category is greater

than ‘negligible’ (noting that there are none in this category at this

stage);

c) KCDC wastewater treatment plant; and

d) All other specifically identified buildings in Condition E.17.

Active construction shall be defined as starting when earthworks

commence within 500m of a particular location and ending when

pavement construction is complete at that location.

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E.21 a) The consent holder shall, subject to the owner’s approval,

undertake a post-construction condition assessment covering the

matters identified in the SEMP and provide a copy to the owner.

The assessment report shall include a determination of the cause

of damage identified (if any) since the pre-construction condition

assessment.

b) The consent holder shall agree with the owner appropriate

remedial works (if any) in conjunction with arrangements for

implementation and/ or compensation. The requirements of this

condition need not be fulfilled for any particular building with the

written approval of the current owner of a building or where the

NZTA can provide reasonable evidence to GWRC that the current

owner of the building has agreed they do not require such a

survey.

E.22 The consent holder shall provide a copy of the pre, post-construction

and any additional building condition assessment reports for each

building be forwarded to the respective property owner within 15

working days of completing the reports. The consent holder shall

notify GWRC that the assessments have been completed.

E.23 Prior to construction commencing, the consent holder shall undertake

CCTV surveys of services identified in the SEMP as being susceptible to

damage or particularly critical. The consent holder shall monitor these

services by undertaking additional CCTV surveys throughout the

construction period. If damage is determined in relation to the Project,

the consent holder shall undertake remedial action as required in

consultation with the service provider.

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